Electrohydraulic pressure regulating device

ABSTRACT

The invention relates to an electrohydraulic pressure regulating device comprising at least one pressure sensor which has a pressure measuring cell and an electronic evaluating circuit for processing measuring signals obtained at a pressure measuring membrane, wherein the evaluating circuit provided for the pressure sensor is arranged on the circuit carrier of the electronic controller which comprises the evaluating circuit necessary for the actuation of the pressure control valve.

TECHNICAL FIELD

The present invention relates to a pressure regulating device, inparticular for motor vehicle brake systems.

BACKGROUND OF THE INVENTION

Electronically controlling brake devices are known in the art (BrakeHandbook, ‘Electronic brake systems’, 1995, ISBN 3-89059-026-8). Theyare composed of a hydraulic control unit, also referred to as valveblock (VB), and an electronic controller (EC). The hydraulic controlunit comprises a motor-and-pump assembly and a valve block flangedthereto. During brake control, the motor-and-pump assembly furnishes thepressurized fluid volume required in the pressure build-up phase. Theinlet and outlet valves grouped in the valve block permit the modulationof the wheel brake pressures. The brake lines leading to the wheelbrakes are connected to the valve block. The valves are connectedhydraulically to the valve block by means of bores. Signals of the fourwheel speed sensors are sent to the controller.

It is possible to improve brake pressure control by the provision of oneor more pressure sensors in the hydraulic lines that lead to the wheelbrake cylinders. The pressure sensors are mounted directly on the valveblock in prior art devices on which the invention is based. Apart frompressure sensors, the valve block comprises, among others,electromagnetically operable hydraulic valves. Electric coils necessaryfor the operation of the hydraulic valves are arranged inside thecontroller. The brake control device is completed in a later assemblystep by joining valve block and controller. To this end, valve block andcontroller are designed as a so-called magnetic plug. In the joiningaction, the coils slide over the hydraulic valves arranged in the valveblock. This action additionally establishes the electrical contactsbetween the pressure sensors arranged in the valve block and the circuitcarrier arranged in the controller by way of spring contacts.

In the prior art device with pressure sensors arranged in the valveblock, the electrical components necessary for the electronicconditioning of the measuring signals received at the pressure sensormembrane are either comprised in a pressure sensor modular unit or, inthe case of several pressure sensors, comprised in a pressure sensormodule. The pressure sensor unit or the pressure sensor module is thusarranged on the valve block and rigidly connected to the valve blockafter the assembly of the valve block.

From this ensues the disadvantage that normally the entire valve blockmust be replaced when one pressure sensor fails. A test for the properfunctioning of the pressure sensor(s) can only be carried out after thevalve block and the controller have been joined. This causesimponderable conditions that can increase manufacturing costs.

DE 197 55 821 A1 discloses a control circuit and a pressure sensoraccommodated in a joint housing of an add-on control device, on thebottom side of which a pressure measuring element with a plug-in pipe isarranged. To form a pressure control device, the plug-in pipe extendsinto a fluid channel of a hydraulic block when the add-on control deviceis fitted. It is complicated under manufacturing technology aspects thatthe hydraulic block includes a blind-end bore, an inserting cone, asupporting disc, and a collecting funnel in the area of the fluidchannel in order to connect the fluid channel to the plug-in pipe. Thiscondition requires sufficient space for the attachment of the pipe inthe hydraulic block in order to establish the connection of the plug-inpipe with the fluid channel. Several pressure sensors with theassociated evaluating circuit are grouped on one common carrier, beingattached as an independent assembly in the add-on control device. Thisfact requires much space and additional effort in testing.

An object of the present invention is to design a pressure regulatingdevice of the type referred to hereinabove in such a fashion that theabove-mentioned shortcomings are avoided.

For the sensor-type scanning of a hydraulic channel with a pressuretransducer, the invention preferably arranges for a structurallyseparate arrangement of the pressure measuring cell, which may, e.g.,comprise a pressure measuring membrane and a passive uncompensated wirestrain gauge, and the electronic circuit for the conditioning of thesignals of the wire strain gauge in the unit of the electroniccontroller.

The electrohydraulic pressure regulating device of the invention iscomprised of a valve block and an electronic controller to form amonolithic unit. Preferably, the two units are configured as magneticplugs.

Thus, the invention obviates the need for the otherwise usualintegration of an active electronic circuit for the pre-amplification ofsignals, for signal conditioning and error compensation of the wirestrain gauge in the modular unit of the pressure sensor.

In a preferred embodiment of the invention, the electronic componentsfor the signal conditioning for one or more pressure transducers arerealized as a part of a larger integrated circuit IC in the controller.

Preferably, the individual signals of all pressure transducers areconditioned in terms of signal technology for conditioning the sensorsignals and subsequently sent to an arithmetic unit. In this operationit is expedient, as will be described hereinbelow, that errorcompensation is not effected within the circuit but within thearithmetic unit.

In another preferred embodiment, the controller incorporates calculationmeans, especially configured as one or more microcomputers ormicrocontrollers that permit minimizing the errors of the measuringchain of each individual pressure channel by the electronic evaluationof two functionally separate calculations of correction variables orcorrection tables. For example, methods for minimizing errors in thetreatment of the pressure measuring signals can be performed with thementioned calculation means. Thus, it is, e.g., possible to determinethe deviations of a pressure transducer as a function of pressure andtemperature and/or the deviations of the signal conditioning stageassociated with the pressure transducer as a function of the signalinput voltage and the temperature by way of point measurements and tomemorize the result of this determination.

Preferably, the device of the invention is implemented inelectrohydraulic brake systems (EHB).

One of the advantages of the invention is that defective pressuresensors can be checked and exchanged at a substantially lower cost dueto the arrangement in the electronic controller than would be the caseif the pressure sensor were mounted on the valve block.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a representation of a modular unit of a pressure regulatingdevice for motor vehicle brake systems comprised of a controller and avalve block.

FIG. 2 is a cross-sectional view of a pressure measuring cell installedinto the housing of the controller.

FIG. 3 is a top view of a pressure measuring cell installed into thehousing of the controller.

FIG. 4 is an embodiment of a pressure-tight connection of a pressuremeasuring cell in a valve block.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a schematically simplified view of an electrohydraulicpressure regulating device 2 for the actuation of hydraulically operatedmotor vehicle brakes composed of a valve block 1 and a controller 3. Thevalve block 1 and controller 3 form a compact modular unit. Valve block1 and controller 3 are connected by way of an electric and magneticinterface (not shown) (so-called magnetic plug). Upon requirement, valveblock 1 conveys pressure-modulated brake fluid to the wheel brakesthrough non-illustrated pressure control valves contained therein, whichare adapted to be actuated by the controller 3. The pressure controlvalves in the valve block 1 are actuated by way of electric coilsaccommodated in the controller 3 and seated onto the so-called valvedomes (valve domes and coils are not shown). The valve coils areelectrically connected to components on a circuit carrier 9 incontroller 3.

Pressure measuring cells 4′ of several pressure sensors 4 are arrangedbeside the valve coils at appropriate positions within housing 6. Forthe sake of clarity, only one pressure sensor 4 is shown. The pressuresensor 4 is held by a web 7 connected to the wall of housing 6, the webbeing made of the material the controller housing is made of. Web 7 hasa thicker wall in the area of the pressure measuring cell 4′ foraccommodating the pressure measuring cell 4′.

The housing 6 of the controller 3 is connected to the valve block 1 byway of at least one operatively and/or positively engaged connectingmeans 16 (screw, rivet, etc.). Controller 3 is secured to valve block 1by connecting means 16.

FIG. 2 shows a pressure measuring cell 4′ of a pressure sensor 4 beingconnected to a tubular supply element 13 that is plugged into a pressureline 5 of valve block 1 when the controller 3 is mounted onto valveblock 1. Sealing with respect to the valve block 1 is carried out by wayof an annular seal 14 that is compressed between a bore step adjacent tothe pressure line 5 and a ring-disc-shaped holding means 12′ connectedto supply element 13. To guide the pressure measuring cell 4′ and thesupply element 13 in web 7, there is provision of two disc-shapedholding means 12, 12′ arranged at the two tubular ends of the tubularsupply element 13. Lamination with the material of web 7 allows a safefixation of the pressure sensor 4 that is formed of the supply element13, the holding means 12, 12′ and the pressure measuring cell 4′ withinweb 7. According to the drawing, the pressure measuring cell 4′ thatcomprises a measuring membrane and wire strain gauges arranged thereonis connected directly to one of the two holding means 12. By way of bondwires 11 or flexible foil, the wire strain gauges are connected to thecircuit carrier 9 that is fixed as a horizontal printed circuit boardabove the web 7 in the frame-shaped housing 6. Circuit carrier 9 carriesthe electronic components of the controller 3 required for both thepressure sensor 4 and for the actuation of the pressure control valves.The printed circuit board made of plastics can be furnished with ametallic cold plate 17 for cooling the electric components. The holdingmeans 12 is connected to the web 7 by spray-coating with a plasticmaterial, additionally forming the housing 6. More specifically,spray-coating may include injection molding a plastic material aroundholding means 12 in the web 7.

Electronic components 8 for evaluating the signals of the pressuremeasuring cell 4′ and a microcontroller 10 are arranged on the circuitcarrier 9.

FIG. 3 shows a top view of web 7 into which a pressure measuring cell 4′is injection-molded. The web 7 is appropriately made of the material ofthe controller housing and is favorably manufactured in one operationwith the controller housing. It is, of course, also possible to attachthe pressure measuring cell 4′ in web 7 in any other way, such as byscrewing, plugging, latching, cementing, or by means of a thermoplasticconnection.

FIG. 4 shows an example for a pressure-tight coupling of a pressuremeasuring cell 4′ to a pressure line 5 in the valve block 1. In thepressure line 5 provided with a step, a plug 15 made of rubber isretained on the end surface of valve block 1 facing web 7, the plugbeing expediently shaped like a nozzle or a similar element so that theplug 15 is fixed in position and additionally forms a sealing surface 18between the valve block 1 and the disc-shaped holding element 12 at thesupply element 13.

When controller 3 and valve block 1 are joined during the assembly, thetubular supply element 13 plunges in a press fit and sealingly into anaxial opening of the plug 15. Additional sealing is achieved bycompressing the disc-shaped sealing surface 18 at plug 15 between theholding means 12 and the valve block 1 as soon as the housing 6 is urgedonto the valve block 1 by means of appropriate fastening means 16. Asthis occurs, it is especially appropriate that the disc-shaped holdingmeans 12 is arranged so that it ends flush in a roughly plane fashionwith the bottom edge 19 of the controller 3 that faces the valve block1.

When there are fewer demands placed on the seal-tightness of theabove-mentioned connection, it can be suitable to design the seal onlyby means of a sealing ring 14 (cf FIG. 2), thereby obviating the needfor a plunging pipe.

The invention disclosed provides a pressure regulating device 2 thatpermits a particularly simple integration of one or more pressuresensors 4 in a housing 6 because the electronics (evaluating circuit 8)necessary for the function of each pressure sensor 4 is arranged on acircuit carrier 9 of the electronic controller 3. The controlleradditionally includes the circuits for the operation of the pressurecontrol valves and, as the case may be, also the circuits for theoperation of a pump motor fitted to the valve block 1. The result isthat all mentioned circuits may be accommodated in an extremely compactway, e.g., on one single printed circuit board, thereby allowing asurprisingly simple function test of all mentioned circuits. Whenever anerror occurs, it is only necessary to exchange the extremely inexpensiveprinted circuit board (circuit carrier 9). A low-cost replacement of theframe-shaped housing 6 can be realized in an equally simple fashion inthe event of a defect in the pressure measuring cell 4′ because thepressure measuring cell 4′ is injection-molded.

1. Electrohydraulic pressure regulating device comprising: a valve blockand an electronic controller, said controller including a housing and acircuit carrier located therein and joined to said valve block to form amodular unit, said housing being formed with a web extending generallyparallel to the outer walls thereof, at least one pressure sensorarranged within said modular unit for detecting the pressure of ahydraulic fluid prevailing in a pressure line of the valve block, saidpressure sensor including a pressure measuring cell carried in said weband being connected to an electronic circuit located on said circuitcarrier for processing measured pressure signals from said cell, atleast one pressure control valve arranged in said valve block, saidpressure control valve being connected to said electronic circuitwhereby it is operated by said electronic circuit, a tubular supplyelement extending through said valve block and terminating at one end ina pressure line and at its other end adjacent said pressure measuringcell, and two holders positively carried in said web, said holder(s)being directly connected to said tubular supply element to retain saidtubular supply element in operative position with said pressuremeasuring cell, wherein each of said holders is in the form of a disc,one of said discs being adjacent the pressure sensor, and the other ofsaid discs being adjacent the valve block.
 2. Pressure regulating deviceas claimed in claim 1, wherein a plurality of pressure sensors arearranged inside the housing of the electronic controller.
 3. Pressureregulating device as claimed in claim 1, wherein the pressure measuringcell is connected to the evaluating circuit by means of flexibleconductors.
 4. Pressure regulating device as claimed in claim 3, whereinthe flexible conductors are contact springs, flexible foils, wires, orbond wires.
 5. Pressure regulating device as claimed in claim 1, whereinthe pressure measuring cell is connected to the housing of theelectronic controller directly and/or by way of the holder(s), and theconnection is made especially by injection-molding a plastic material ofthe housing.
 6. Pressure regulating device as claimed in claim 1,wherein several electronic circuits of several pressure sensors aregrouped in an integrated circuit on the circuit carrier provided for thepressure control valve.
 7. Pressure regulating device as claimed inclaim 6, wherein an output signal of the electronic unit is sent to anarithmetic unit.
 8. Pressure regulating device as claimed in claim 1,wherein the pressure sensor measuring cell and/or holder(s) connectedoperatively and/or positively to the pressure sensor is joined at a webconnected to the housing.
 9. Pressure regulating device as claimed inclaim 1, wherein the holding means is connected to the web byspray-coated plastic material.
 10. Pressure regulating device as claimedin claim 1, wherein the tubular supply element and/or the holder(s)establishes a pressure-tight connection to the valve block by way of aseal that has an annular shape.
 11. Pressure regulating device asclaimed in claim 1, wherein the tubular supply element and/or theholder(s) establishes a pressure-tight connection to the valve block byway of a seal that has a plug-like shape.